使用ChArUco对两台摄像机进行OpenCV立体标定

Question

我想使用acharuco board的多个帧计算两个相机之间的相对变换（[R|t]矩阵）。我的想法是从所有帧中获取图像对象点对，然后使用一个函数获取所有检测到的点对并输出相机之间的相对变换（例如stereoCalibrate）

最好的方法是什么？我无法让stereoCalibrate工作，因为它总是抛出断言错误->bugreport

当前实施（不起作用）：

imagePointsA = []
imagePointsB = []
objectPoints = []
    for frameA, frameB in color_framesets(...):
        try:            
            # Find corners
            cornersA, idsA, rejected = cv2.aruco.detectMarkers(frameA, charucoDict)
            cornersB, idsB, rejected = cv2.aruco.detectMarkers(frameB, charucoDict)
            if not cornersA or not cornersB: raise Exception("No markers detected")

            retA, cornersA, idsA = cv2.aruco.interpolateCornersCharuco(cornersA, idsA, frameA, charucoBoard)
            retB, cornersB, idsB = cv2.aruco.interpolateCornersCharuco(cornersB, idsB, frameB, charucoBoard)
            if not retA or not retB: raise Exception("Can't interpolate corners")


            # Find common points in both frames (is there a nicer way?)
            objPtsA, imgPtsA = cv2.aruco.getBoardObjectAndImagePoints(charucoBoard, cornersA, idsA)
            objPtsB, imgPtsB = cv2.aruco.getBoardObjectAndImagePoints(charucoBoard, cornersB, idsB)

            # Create dictionary for each frame objectPoint:imagePoint
            ptsA = {tuple(a):tuple(b) for a, b in zip(objPtsA[:,0], imgPtsA[:,0])}
            ptsB = {tuple(a):tuple(b) for a, b in zip(objPtsB[:,0], imgPtsB[:,0])}
            common = set(ptsA.keys()) & set(ptsB.keys())    # intersection between obj points
            
            for objP in common:
                objectPoints.append(np.reshape(objP, (1, 3)))
                imagePointsA.append(np.reshape(ptsA[objP], (1, 2)))
                imagePointsB.append(np.reshape(ptsB[objP], (1, 2)))

        except Exception as e:
            print(f"Skipped frame: {e}")
            continue

    result = cv2.stereoCalibrateExtended(objectPoints, imagePointsA, imagePointsB, intrA, distA, intrB, distB, (848, 480), flags=cv2.CALIB_FIX_INTRINSIC+cv2.CALIB_USE_EXTRINSIC_GUESS)
   

Answer 1

今天早些时候，我刚刚做了类似的事情。我认为您至少解决了部分问题，因为您关闭了提到的bug。在任何情况下，在我看来，问题在于您传递的是一个点数组，而它应该是一个点数组（具有足够数据的每个帧的点数组）

另一方面，cv2.aruco.getBoardObjectAndImagePoints可能不是您想要的，因为cornersA和cornersB已经是图像点（棋盘图案角），对象点（棋盘图案角的位置）可以从aruco标记ID计算，而getBoardObjectAndImagePoints就我所知是关于aruco标记角的

在内部，cv2.aruco.calibrateCameraCharuco只调用cv2.calibrateCamera，将传递的角点作为图像点，对象点computed from the passed aruco IDs。不幸的是，从aruco ID获取对象点并没有在API中公开，但它非常容易计算：https://github.com/opencv/opencv_contrib/blob/master/modules/aruco/src/charuco.cpp#L157-L166